Cleverley, William O., author
Aspen Publication, 1997
Buku Teks
Cleverley, William O., author
Jones Bartlett Learning, 2011
Buku Teks
Akin, John S., author
World Bank, 1987
Buku Teks
Harrison, Carlene, author
Delmar Cengage Learning, 2013
Buku Teks
Cushman, Robert F., author
An Aspen Publication, 1983
Buku Teks